The ROADM system is known as a network technology for controlling wavelengths, which carries signals, through a whole of network by combining the wavelength multiplexing art and the path management art, so that a super high speed transmission network with a large amount of capacity can be operated. ROADM is an abbreviation of “Reconfigurable Optical Add Drop Multiplexer”. Hereinafter, the ROADM system may be called “system” for simplicity.
A ROADM system related to the present application will be described with reference to FIG. 7. FIG. 7 is a block diagram showing a configuration of a ROADM node 900 related to the present application.
The ROADM node 900, which is an optical node apparatus, can connect with n-routing (n-directional) optical transmission lines, where n is integer not less than 2. The ROADM node 900 realizes the colorless (wavelength-independent) function, the directionless (not depending on route) function and the contentionless (not depending on contention) function. The ROADM node 900 is an exemplified ROADM node which has a configuration that a transponder unit 941 can connect with any connection port, any route and any wavelength.
The ROADM node 900 includes an apparatus controlling and managing unit 901, a plurality of optical cross-connect units 911 and 912, a plurality of wavelength selecting units 921 and 922, a light splitting and selecting unit 931, and the transponder unit 941.
Connections between the optical cross-connect units 911 and 912, and the wavelength selecting units 921 and 922 respectively, and between the wavelength selecting units 921 and 922, and the light splitting and selecting units 931, and between the light splitting and selecting units 931 and the transponder unit 941 are formed through optical patch cords. The optical patch cord is a short cable with connectors on both ends. To check the connection through the optical patch cord is carried out by the worker's visual inspection.
FIG. 7 shows a configuration of the ROADM node 900 in which a main signal to carry user's information is amplified optically and sent into an optical transmission line B or an optical transmission line C out of n routes. A sending side amplifying part 918 and a sending side amplifying part 920 amplify the main signals optically, and the amplified signals are sent into the optical transmission line B and the optical transmission line C respectively.
Moreover, according to FIG. 7, a receiving side amplifying part 913 or a receiving side amplifying part 914 receives an input signal (main signal) from another node through an optical transmission line A or an optical transmission line D respectively. The received main signal is amplified optically and transferred to the inside of the ROADM node 900. An operation of the ROADM node 900 for each route other than the optical transmission line A and the optical transmission line C is the same as one for the optical transmission line A or the optical transmission line C. Similarly, an operation of the ROADM node 900 for each route other than the optical transmission line B and the optical transmission line D is the same as one for the optical transmission line B or the optical transmission line D.
First, an operation of dropping an optical signal in the ROADM node 900 will be described. The receiving side amplifying part 913 and the receiving side amplifying part 914 of the ROADM node 900, each of which has an optical amplifying function, receive the input signals (main signals) from other nodes through the optical transmission line A and the optical transmission line D respectively out of n routes. Then, the receiving side amplifying part 913 and the receiving side amplifying part 914 amplify the main signals and transfer the amplified main signals to light distributing parts 915 and 916 respectively.
The signal, which is outputted by the receiving side amplifying part 913, is passed through the light distributing part 915, a wavelength selecting part 923 and a receiving light splitting unit 932 to reach to a receiving light switching part 933. The signal, which is outputted by the receiving side amplifying part 914, is passed through the light distributing part 916, a wavelength selecting part 924 and a receiving light splitting part 934 to reach to the receiving light switching part 933. The receiving light switching part 933 selects a signal, which is transferred to a main signal receiving part 942, out of signals received through a plurality of routes, and transfers the selected signal to the main signal receiving part 942.
The main signal receiving part 942 receives a wavelength assigned to the main signal.
The apparatus controlling and managing unit 901 carries out control to send a connection detecting light and to stop sending the connection detecting light, and checks whether an expected connection destination receives the connection detecting light, and judges normality on the connection on the basis of a result of the check. If the apparatus controlling and managing unit 901 can not judge that the connection is normal, the apparatus controlling and managing unit 901 notifies a user of an alert, and advises the user of checking and correcting the connection.
In the case that the apparatus controlling and managing unit 901 judges that a point not connected exists or an optical connector becomes soiled, the apparatus controlling and managing unit 901 notifies the user of the alert, and advises the user of carrying out a work for connecting the units or a work of cleaning the optical connector.
Next, an operation of adding an optical signal in the ROADM node 900 will be described. An output port of a main signal sending part 943 of the transponder unit 941 is connected with a sending light switching part 935 of the light splitting and selecting unit 931. The sending light switching part 935 has a function to select a connection route out of a plurality of routes between the sending light switching part 935 and a sending light splitting part 936 and between the sending light switching unit 935 and a sending light splitting part 937, and sends the signal into the selected route.
A signal, which is outputted by the main signal sending part 943, is passed through the sending light switching part 935, the sending light splitting part 936, an optical coupler part 925 and a wavelength selecting and connecting part 917 to reach to the sending side amplifying part 918. Or, the signal, which is outputted by the main signal sending part 943, is passed through the sending light switching part 935, the sending light splitting part 937, an optical coupler part 926 and a wavelength selecting and connecting part 919 to reach to the sending side amplifying part 920.
The wavelength selecting and connecting part 917 transfers the main signal, which is provided by the optical coupler part 925, toward the sending side amplifying part 918.
Moreover, the wavelength selecting and connecting part 919 transfers the main signal, which is provided by the optical coupler part 926, toward the sending side amplifying part 920.
The apparatus controlling and managing unit 901 carries out the control to send the connection detecting light and to stop sending the connection detecting light. Moreover, the apparatus controlling and managing unit 901 checks whether an expected connection destination receives the connection detecting light, and judges the normality on the connection on the basis of a result of the check. If the apparatus controlling and managing unit 901 can not judge that the connection is normal, the apparatus controlling and managing unit 901 issues a rumbling alert, and advices the user of checking and correcting the connection.
In the case that a reflection light is detected, the apparatus controlling and managing unit 901 judges that a point not connected exists or an optical connector becomes soiled, and consequently the apparatus controlling and managing unit 901 issues the rumbling alert, and advises the user of carrying out the work for the connection or the work of cleaning the optical connector.
Due to the colorless function, the directionless function and the contentionless function of the ROADM node 900, it is complicated to arrange an optical path through setting an adding and dropping of the optical wavelength. For this reason, it is complicated to connect the internal units each other through the optical patch cord, and it is not easy to check the normality on the connection. As a result, a false connection is caused, and furthermore interference with the operative main signal is caused due to the false connection. Then, a communication failure may be caused in some cases.
Furthermore, it is possible that the above-mentioned ROADM node can connect with the n-routing optical transmission lines and realize the colorless function, the directionless function and the contentionless function. Moreover, it is possible that the transponder unit connects with any connection port, any route and any wavelength. For this reason, it is possible that the ROADM node connects with any connection port, any route and any wavelength through connecting the internal units each other through the optical patch cord and setting the adding and dropping of the optical wavelength. However, a work of checking whether the optical patch cord is connected correctly is carried out by the worker's visual inspection. Japanese Patent Publication No. 4500136, which is related to the present invention, describes a configuration of an optical transmitter which has a function to detect the false connection.